Thyroid gland
General
Cytology / fine needle aspiration


Topic Completed: 31 May 2019

Revised: 10 June 2019

Copyright: 2003-2019, PathologyOutlines.com, Inc.

PubMed Search: "Fine needle aspiration"[title] cytology thyroid (Review[ptyp] "loattrfree full text"[sb])


Rachel Jug, M.B.B.Ch.
Xiaoyin
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Cite this page: Jug R, Jiang X. Cytology / fine needle aspiration. PathologyOutlines.com website. http://www.pathologyoutlines.com/topic/thyroidcytology.html. Accessed September 23rd, 2019.
Definition / general
  • Minimally invasive technique to obtain cytologic specimens of thyroid nodules
  • Thyroid fine needle aspiration (FNA) was introduced in 1930 by Martin and Ellis who used an 18 gauge needle aspiration technique; however, it became a mainstream approach much later, after introducing of so—called small needle aspiration biopsy (now referred to as fine needle aspiration) (Ann Surg 1930;92:169)
  • Recommended procedure when evaluating thyroid nodules for malignancy to triage patients for possible surgery (Thyroid 2016;26:1)
  • Can be performed using palpation guidance or ultrasound guidance
  • Results recommended to be reported in standardized format using the Bethesda System for Reporting Thyroid Cytopathology (see Bethesda categories)
  • Sensitivity and specificity of fine needle aspiration have been reported as high as 100% and 94%, respectively, if specimen is adequate; larger nodules have been reported to have higher false negative rate (PLoS One 2017;12:e0186242, BMC Res Notes 2008;1:12)
Essential features
  • Superficial thyroid nodules may be targeted by palpation (if palpable) or ultrasound (nonpalpable or complex) guidance with minimal complication
  • Rapid on site evaluation (ROSE) may be performed to assess specimen adequacy
  • Thyroid fine needle aspiration is a highly accurate diagnostic procedure with few complications
  • The Bethesda System for Reporting Thyroid Cytopathology is the recommended system to report results
Terminology
  • Fine needle aspiration, thin needle aspiration, ultrasound guided fine needle aspiration or palpation guided fine needle aspiration
CPT coding
  • 10021 - fine needle aspiration
  • 10022 - fine needle aspiration using imaging guidance
  • 88112 - cytopathology, selective cellular enhancement technique with interpretation (eg, liquid based slide preparation method), except cervical or vaginal (ThinPrep / SurePath technique)
  • 88172 - cytohistologic evaluation of fine needle aspirate to determine adequacy for diagnosis
  • 88173 - cytopathology, evaluation of fine needle aspirate; interpretation and report
  • 88177 - cytohistologic evaluation of fine needle aspirate to determine adequacy for diagnosis (additional passes)
Epidemiology
Sites
  • In addition to presenting in the thyroid parenchyma, thyroid nodules may present as lymph nodes or other neck lesions, as there can be ectopic thyroid or parasitic nodules in thyroiditis
  • Nodule location within thyroid gland should be confirmed by ultrasound to avoid unintentional biopsy of adjacent tissues (Diagn Cytopathol 2008;36:390)
Diagrams / tables

Contributed by Rachel Jug, M.B.B.Ch.

Risk based on appearance and nodule characteristics

Ultrasound fine needle aspiration techniques



Images hosted on other servers:

Technique

Short rapid strokes
with only slight
changes in direction

Indications (stratified by approach)
Palpation guided Ultrasound guided
Incidentally or radiographically identified predominantly solid (> 75%) thyroid nodule > 1 cm diameter confirmed by ultrasound Complex and cystic nodules (> 25% cystic component); ultrasound helps target specific areas, such as solid areas (Diagn Cytopathol 2008;36:390)
Thyroid nodule of interest is discrete and palpable Nonpalpable or difficult to palpate nodules (e.g., posteriorly located) (Diagn Cytopathol 2008;36:390)
Limited access to ultrasound guided fine needle aspiration, palpation guided fine needle aspiration may be considered (Diagn Cytopathol 2008;36:390) To aid skilled operator in ascertaining sample of specific nodule of interest and to avoid adjacent critical structures (Diagn Cytopathol 2008;36:390)
For repeat fine needle aspiration, when a prior palpation guided fine needle aspiration sample was insufficient (Diagn Cytopathol 2008;36:390)
Followup for patients post partial or total thyroidectomy for malignancy, such as to sample thyroid bed (J Ultrasound Med 2013;32:1319)


  • 2015 American Thyroid Association (ATA) Management Guidelines for Adult Patients with Thyroid Nodules and Differentiated Thyroid Cancer
    • Strongly recommend ultrasonic examination of thyroid and cervical lymph nodes of thyroid nodules
    • Recommended sampling if > 1 cm in greatest dimension and high suspicion sonographic pattern (estimates a 70% - 90% risk of malignancy), including solid hypoechoic nodule or nodule that is partially solid and hypoechoic and partially cystic with one or more of the following features:
      • Irregular margins (infiltrative, microlobulated)
      • Microcalcifications
      • Oval (taller than wide) shape
      • Rim calcifications with an extrusive soft tissue component
      • Evidence of extrathyroidal extension (Thyroid 2016;26:1)
Contraindications
  • Relative contraindications:
    • Unable to lie recumbent
    • Unable to control their rate and depth of respiration adequacy
    • Severe anxiety (reassure variable anxiolytics)
    • Young children (may require sedation)
    • On heparin, warfarin, clopidogrel, high dose aspirin and other anticoagulants (Baskin: Thyroid Ultrasound and Ultrasound-Guided FNA, 2nd Edition, 2008)
    • Variant anatomy due to previous illness or surgery
    • Nodule of interest is hot on radionuclide thyroid scan
    • Goiter (diffuse or asymmetric) precluding localization of nodule of interest (Diagn Cytopathol 2008;36:390)
  • Absolute contraindication: severe coagulopathy disorder
Benefits of ultrasound guided fine needle aspiration compared to conventional fine needle aspiration alone
Core biopsies
  • Core biopsies are not the preferred initial procedure of choice in evaluation of a concerning thyroid nodule as per ATA 2015 guidelines (Thyroid 2016;26:1)
  • Core biopsies may be useful for fibrotic nodules that yield inadequate samples on repeat fine needle aspiration or for collecting additional material for ancillary testing (Endocrinol Metab (Seoul) 2017;32:407)
Set up
  • Position patient supine with neck extended and pillow under shoulders
  • Examine the thyroid lobes and neck for thyroid masses and lymphadenopathy
  • Assess the size of suspicious nodules identified to help select fine needle aspiration needle size and length to obtain an appropriate sample (Baskin: Thyroid Ultrasound and Ultrasound-Guided FNA, 2nd Edition, 2008)
Needle based sample collection techniques
  • Prior to aspiration with needle, use nondominant hand to stabilize the nodule and pull the skin taught between stabilizing fingers; clean the site with alcohol and let it dry prior to needle entry to prevent stinging
  • Approach the skin at 45 degree angle with needle
  • Local anesthetic with buffered lidocaine may be used but is not necessary (and adds an extra needle stick that may compromise cytology) since the majority of patients do not report pain after the procedure (J Emerg Med 1992;10:411, J Pain Res 2017;11:61)
  • With aspiration / suction
    • 27 or 25G needle attached to a 10 cc syringe (with or without extension tubing) withdrawn so that 1 - 2 cc of negative pressure induces aspiration
  • Without aspiration / nonsuction
    • 27 or 25G needle (with or without stylet, may attach open syringe) is introduced into nodule and capillary action causes uptake of cellular material into the needle
    • Systematic review and meta-analysis concluded superiority of thyroid fine needle aspiration with smaller needle gauges (24 - 27G) and without aspiration (Thyroid 2018;28:857)
    • May opt to use larger needle (22G) in severely calcified nodules to prevent bending of smaller needles within the lesion (Endocr J 2019;66:143)
    • Use of a bare needle without a syringe or negative suction is termed the Zajdela technique which capitalizes on the capillary action induced by forward motion of the needle in contrast to the application of suction (by syringe with or without a syringe holder)
  • Regardless of the method, immobilization of the target while completing multiple passes rapidly through the lesion in a fanning motion is required to adequately sample the lesion (Diagn Cytopathol 2008;36:407)
Sample preparation
  • Sample preparation depends on the institution's preferred method
  • Preparation methods include smears (air dried and alcohol fixed), liquid based preparations (ThinPrep, SurePath, etc.) and cell block
  • For air dried slides, the Romanowsky staining method (using a stain such as Diff-Quik) is commonly used and alcohol fixed smears prevent drying artifacts and may be stained with the Papanicolaou stain
  • For cases with rapid on site evaluation for adequacy, air dried slides can be used to evaluate material
  • If a pathologist is not present to perform the fine needle aspiration or to provide rapid on site evaluation, the institution may prefer to prepare exclusively Papanicolaou stained or ThinPrep slides.
  • Additional material for ancillary tests, including, biochemical and molecular testing (see Thyroid gland - Molecular testing in FNA) may be collected; the latter into nucleic acid preservative solution at the time of all initial thyroid biopsies or at the time of repeat sampling of an indeterminate nodule
  • Additional material for tests such as thyroglobulin washout, calcitonin, etc. may collected as appropriate
  • Tips: if samples are very bloody, consider placing excess blood / clot into a liquid based sample vial or making cell block, rather than making multiple bloody smears; follicular epithelium may get stuck in needle hubs – needle shield devices may be used to help flick excess material out of needle hub safely
Complications
Treatment
  • Following the fine needle aspiration procedure, ultrasound may be utilized to scan the neck for potential complications before they become apparent and prior to the patient leaving the clinic / hospital (AJSP: Reviews & Reports 2018;23:165)
  • Patient should be reminded of aftercare:
    • Acetaminophen and icing may be used to relieve pain and swelling in accordance to medication directions on the packaging if they do not have contraindications
    If bleeding is profuse or massive swelling occurs, patients should present to urgent care or emergency department for further evaluation
Diagnosis
  • Comparison of procedural ultrasound is made with diagnostic ultrasound to corroborate lesion of interest; findings on diagnostic ultrasound contribute to risk stratification of thyroid lesions in accordance with the 2015 ATA Management Guidelines (see Thyroid gland - Ultrasound) (Thyroid 2016;26:1)
  • Diagnostic categories are assigned based on the Bethesda Categorization of Thyroid Nodule Cytology and Prediction of Thyroid Cancer Type and Prognosis (Thyroid 2016;26:256)
Radiology description
Radiology images
Molecular / cytogenetics description
Molecular / cytogenetics images
Videos

FNA biopsy techniques

Thyroid FNA and smearing techniques


Superficial FNA technique

Sample pathology report
Board review question #1
What type of sample is evaluated during a rapid on site evaluation of a thyroid fine needle aspiration?

  1. Air dried stained slide
  2. Cell block material
  3. Core biopsy slide
  4. SurePath slide
  5. ThinPrep slide
Board review answer #1
A. Air dried stained slide – air dried slides are ideal for rapid on site evaluation.

Reference: Thyroid gland - Cytology / fine needle aspiration

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Board review question #2
Which of the following fine needle aspiration indications would favor using ultrasound guided rather than palpation guided fine needle aspiration?

  1. First biopsy of the specific lesion in question
  2. Patient referred specifically for fine needle aspiration with rapid on site evaluation
  3. Predominantly solid nodule
  4. Superficial thyroid nodule > 1 cm
  5. Thyroid nodule of interest in background of a multinodular goiter
Board review answer #2
E. Thyroid nodule of interest in background of a multinodular goiter – ultrasound guidance will assist in localizing fine needle aspiration to nodule of interest as opposed to off-target nodules with benign radiographic features. Ultrasound guided fine needle aspiration allows for real time correlation to diagnostic ultrasound images.

Reference: Thyroid gland - Cytology / fine needle aspiration

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